Metallurgical method and apparatus



a. F. GREENWOOD.

METALLURGICAL METHOD AND APPARATUS.

APPLICATION FILED lULYl9,1-918.

Patented Apr. 27, 1920.

2 SHEETS-SHEET I.

G. F. GREENWOOD.

METALLURGICAL METHOD AND APPARATUS.

APPLICATION FILED JULY 19, 1918.

' 1,338,439. Patented Apr. 27, 1920.

2 SHEEISSHEE1 2.

a vwewtoz W '3 $3M imme I UNITED STATES PATENT cur os.-

.GUYON I. GREENWOOD, OF GEORGEVILLE, QUEBEC, CANADA.

METALLURGICAL METHOD AND APPARATUS.

To all'wlwm it may concern:

.' Be it known that I, GUYoN' F. GnnEN improved method and system forroasting, v reducing and refining oxid, carbonate and other ores, themaking of coke and similar' processes.

The object of my invention is to greatly" reduce the amount of coal orcarbon required per ton of metal, to improve'the quality of the metalreduced, to reduce-thecost of the required plant, its maintenance andthe labor cost of the product and to materially increase the by-productvalue.

It has been shown experimentally that "there are certain pressures andtemperatures of the equilibria phenomenon occurring in the reduction ofoxid ores ifsufiicient solid carbon is present, such that substantiallyany carbon dioxid produced or present will [disappear and take the formof carbon 7 monoxid where 'the reduction is carried on with exclusion ofair, and I have therefore designed and constructed a furnace which willperform the required mechanical operations and maintain the pressure andtemperatures indicated as necessary.

The first requirement for high efiiciency in this reduction system isthe substantial elimination of carbon dioxid and the sub-' stitution ofcarbonmonoxid, as the gas resulting' from. the reaction, This isespecially true Wit'lldI'OIl oxids, and holds with I the others also,while for any other similar purposes the value of my improved furnacewill readily beseenfrom the following detailed description. Beforedescribing in detail, the method and apparatus involved in thisinvention, I shall briefly refer to present practice in the iron andsteel industry, so that a better conception of the improvementscontemplate-d will be gained.

In general it may be statedthat the entire production of iron frornorein this country at the present time, starts'with the production of pigiron in the blast furnace, the

furnace being chargedwith a'mixture of ore, carbon in some form, and aflux, usually in the form of llme-orlimestone." The car- Speeificationof Letters-Patent.

Patented Apr. 27 1920.

Application filed July 19, 1918. SeriaINo. 245,692.

bon serves as reducing agent and as fuel I for generating the requiredtemperature and supplying the chemical heatunits involved twyers tomaintain combustion of the fue1- for generating the heat as described.The

materials charged into the blast furnace must be in the form of lumps ofsuitable size and dimensions to permit the passage of gases upwardlythrough the furnace, and the depth or height of the charge must besufiicient to provide the necessary space for progressive chemicalactions between the gases and the charge as the gases pass upwardlythrough the same. Furthermore, the height of the furnace is prescribedor determined by considerationsof heat economy and pressure due toweight ,'of the column of charge so as to feed properly by gravity. Theresult has been the development of blast furnaces along the lines ofrelatively great dimensions involving, the

treatment of a large quantity of charge at blast furnace remains theapproved and universallyr employed device for reducmgthe 90 a ore.

The gases comingfrom the blast furnaee contain carbon monoxid, carbondiojriid, n1- trogen, and other components. The more carbon dioxidpresent in the waste gases, the

greater is the fuel and heat efficiency presumed-t0 be. The combustionof carbon being an exothermic chemical action, not only in the stageof-carbon to carbon monoxid, but also from the carbon monoxid to carbondioxid, it is obvious that the pres cenceof carbon dioxid represents twoquantities of chemical heat units, whereas carbon monoxid represents butone. On the other hand, the carbon dioxid is reducible by lIOIl tocarbon monoxid, so that the presence of the formerunder-certaintemperature conditions, where reduced iron is also present,

has the tendency toreoxidize the iron. The result is that the blastfurnace practlce recognizes a zone condition where these gases, on theirpassage upward through the charge, are reacting with the charge perhapsseveral times one way or the other.

My invention provides an economical furnace and method for reducing oxidores economy of fuel is gained, and a much better control of the purityof the product is assured, while at the same time the relatively complexand expensive blast furnace installation is entirely avoided.Furthermore, the furnace can be run with crushed or ground ore takenfrom the run of the mine and crushed or ground coke or charcoal, insteadof requiring lumps of particular dimensions as in the blast furnace.

The principle of the invention involves the recognition that economy andcertainty of operation are gained by limiting the supply of carbon tosubstantially that required as a reducing agent, and excluding air fromthe reduction step. 'Due to the exclusion of air, and the regulation ofthe temperature and pressure in the reducing chamber, the resultinggases are so regulated as to be constituted almost entirely of carbonmonoxid undiluted with carbon dioxid or nitrogen, with the result that ahighly advantageous form of fuel for generating electrical power is thusprovided, and this power is employed in maintaining the necessaryfurnace temperature for conducting the reduction operation.

So far as I am awareit is broadly new to operate a reduction furnaceunder exclusion of air, and with control of the temperature andpressure, whereby the generation of a highly e'flicient fuel gas, freefrom nitrogen and carbon dioxid is secured in suflicient quantity of aquality that will provide the power to produce the necessary quantity ofelectrical energy for supplying the heat required in the reducing step.

To make the invention clearly understood, I shall describe a specificembodiment thereof, in connection with the accompanying drawing, inwhich,

Figure 1 represents diagrammatically a system involving the reductiondrum, poiver plant and fusion and refining furnace;

Fig. 2 is a longitudinal sectional detail of a preferred construction ofreduction drum, involving an electrical resister;

Fig. 3 is a detail, perspectively, of a portion of the resister to beincorporated in the lining of the reduction furnace.

Fig. 4 is a diagram of a system including a coking furnace.

WVe may consider a case in which the invention is applied, for example,to the reduction of hematite iron ore, previously crushed or ground, andpreheated to a tGII1- perature of about 600 C. and suitable quantitiesof some form of carbon to serve as the reducing agent and a flux to actas a catalyzer and purifier. This mixture is introduced through the feedbell or hopper 10, and passes through the neck 11 into the rotary drum12. Any approved type of union 13 is assumed to be provided forconnecting the stationary neck 11 with the rotary drum proper 12, and,similarly, a union 1% permits the discharge of the reduced materialthrough a discharge neck or chute 15, provided with bell valve 16. Thedrum 12 is set at a suitable inclination and is provided with flanges 17which run on rollers 18, journaled in standards 19. A gear collar 20meshes with a pinion 21 which is driven through suitable powerconnections so. as to slowly rotate the drum 12 upon its longitudinalaxis. The drum is lined, as indicated at 22, with suitable refractorymaterial, such as magnesite brick or burnt magnesite, in which isembedded a helical resister 23, which may advantageously have the crosssectional form of a trapezoid, the base of which is flush with the innerwall of the furnace lining, so that the resister, due to its shape,assists in holding the lining in place, but does not cause anyobstruction to the free passage of the charge of ore, carbon and fluxthrough the furnace. Mechanically considered, the drum represents arotary device by which the charge is caused to slowly progress, from oneend to the other, over the turns or convolutions of a heating resisterelement, the travel of the ore being caused'by the inclination of thedrum and its rotary motion, which is continuously raising and tumblingthe charge, thus thoroughly mixing and distributing the constitutentparts. Electrically considered, the rotary drum constitutes an electricfurnace, of the resister type, in which the resister is in the form of ahelical conductor through which a current is passed and by which adesired quantity of heat is produced, while, at the same time, it servesas a means for introducing current through the charge from oneconvolution to the next, the bridging particles of charge shunting alarge portion of the current through the short circuit thus established,which greatly facilitates and renders verv uniform, the heating action.The electrical action is thus complex in its nature, part of it beingrepresented in simple production of heat by the flow of current againstthe resistance of element 23, whereas an addi tional heating functiontakes place in the short circuit current passing through the charge,from one convolution to another. As the ore becomes more and morereduced its conductivity increases, so that the short circuit effecttends to develop progressively in the drum from the receiving end towardthe discharge end. At the same time, however,- the temperaturecoelficient of thereduc'ed metal causes a decrease in conductiv- 5 itywith increased temperature, so that the short circuit effect isautomatically controlled by. the chemical action as it progresses. Theresult of this complex action is that the operator is enabled, bysuitable regulation of the current passing through the resister, to thusindirectly control the temperature and assure the desired'chemicalaction. For the purpose of supplying current to the resister-23', aterminal 24, 'is connected with the resister at one end, being insertedfor example in an insulating bushing 2 1 mounted in the drum wall andlining. A similar terminal may be employed at the other end of thiscoil. Itis preferable, but not essential to have the entire coilconnected in series relation throughout its entire length rather than tohave it subdivided electrically into parallel portions. The terminals 24are in the present example elec 25 trically connected with slip rings25, mounted on the outer wall of the drum 12 and engaged bybrushes 26,which are electrically connected through conductors 27, 28, with theterminals 30, of a dynamo electric machine 31 of suitable power. Thedynamo 31 is, for example, driven by shaft 32 of gas engine 33. Thisengine may be of any desired type. The engine is shown purely indiagrammatic form and is intended to re- 35 ceive its gas through intakepipe 35 and discharge its exhaust through pipe 36, which is .here shownas being delivered through the incoming charge of materials going to thereduction furnace, for preheating the same.

Mixed with air, in any approved manner, the gases drawn through theoutlet 37 from drum 12 and freed from dust in the dust collector 38,constitute a valuable fuel mixture, as will be more apparent upondetailed consideration of the chemistry involved in the reductionoperation taking place within .drum 12. V The drum 12 has approximatelyair tight .connection with the feeding in and discharging conduits, sothat the suction action of the engine 23 has the effect of maintaining areduced pressure within the drum and as fast as carbon monoxid isproduced by the reduction of the ore with the solid carbon, this carbonmonoxid is withdrawn and taken in by the engine as fuel for generatingelectrical power. The

production of carbon monoxid depends solely upon the chemicalcombination; of the solid carbon and the oxygen of the ore, when theseelements are brought together at a temperature and under a pressurewithin the limits of variation that eliminate carbon dioxid andfacilitate the production of carbon monoxid. By maintaining the tempera-O ture at about 750 C. and the pressure somewhatbelow-atmospheric,"conditions favorable to the production of monoxid areassured and the production of carbon dioxid substantially ceases. Theconstant with- 7 drawal of gas as fast as it is produced, gives therequired reduction of pressure, removes the carbon monoxid rapidly awayfrom exposure to any iron oxid, and thus further tends to avoid formingthe dioxid, or reoxidizing the metal. It is evident that any suitableform of rheostat R in'the circuit with the resister 23 will giveadequate control of the temperature within the reduction drum. Thepressure within the re- I duction chamber may, for example, becontrolled by the speed of the engine 33.

With regard to the chemical heat units, the heat generated in theproduction of carbon monoxid is less than that consumed in reducing theiron oxid. These heat units may be seen from the following formula andtables; in which a temperature of 15 C. is assumed, for simplicity.

The reaction represents a deficit of 108,120 heat units. In order tomake up this deficit and to balance extraneous heat losses such 5 asradiation, etc., electrical energy is consumed in the resister furnace.The tendency of the chemical action to result in .a reduction oftemperature enables the operator to control the temperature at thedesired point 0 by supplying heat through electrical power.Theoretically, the heat required for the chemical action to continuewithout change of temperature is shown by the above equation to be108,120 calories. The combustion of carbon monoxid to carbon dioxid inthe gas engine theoretically renders available nearly twice the quantityof heat electrically required to maintain the reduction action in theresister furnace, as indicated by the following:

' 3OO+3OI3CO or 3 (00,0) =2o4,120

' and the total heat produced is 291,600, thus leaving an excess of96,000 heat units.

The gas engine, or for example, the Diesel type injects the carbonmonoxid gas into the compressed air within the cylinder, developingmechanical power from the available heat energy of the reaction. Theelectrical generator being on the same shaft with the gas enginetranslates its mechanical energy into electrical energy and supplies itto the electrical heating element, namely, the helical coil 23 withinthe rotary drum 12.

In addition to the reaction between iron oxid and carbon, taking placewithin drum 12 there are further reactions which must be provided for infigurin the quantity of carbon in the mixture. The ore contains, forexample, in many instances, compounds of manganese and of magnesium andcan be readily figured by the skilled metallurgist and taken care of inmaking up the proportions of the ingredients which go into the charge.The present invention is not directed particularly to these additionaldetails and it is thou ht the above description of the reduction of ironoxid will suffice to make the invention clear. I

With regard to the flux introduced with the charge, it is, of course,obvious that either limestone or burnt lime may be used; but in one caseheat units represented in driving off carbon dioxid from the carbonateand reducing the carbon dioxid with carbon, would have to be figured inthe re,- duction furnacevoperation, whereas in the other they arealready supplied prior to the reduction. The charge is not fused in thereduction furnace, but is delivered through the discharge passage 15into some suitable form of fusing and refining furnace, (representeddiagrammatically in the form of an electric furnace 39.)

In this furnace the charge is melted, the impurities slagged off and thereduced molten metal obtained. This final treatment of the reduced oredoes not, in itself, constitute a feature of the present invention andneed not be described in'detail, especially as it will vary considerablyaccording to the particular requirements of each case.

The heat units roughly indicated to be available in the abovecomparisons are of course, not all recoverable. in practice. Theefficiency of the engine, for instance, will determine what percentagecan be actually secured. I do not, therefore, want to be limited tocomplete dependence upon'the heat units available from combustion of thegas from the reduction drum. I may desire to use outside power to makeup any difference which may appear due to inefficiency of the engine.referably, however, where it is desired to make the system entirelyindependent of outside electric power, I'may carry out the invention asshown diagrammatically in .Fig. 4.

In 4, the numeral 40 designates a coal supply bin or hopper, from whichcoal is fed to a rotary drum furnace 41, similar to the reducing furnace12, where it' is electrically heated, with exclusion of air, to driveoff a combustible gas" and produce coke. The gas is withdrawn throughpipe 42, and scrubber or tar remover 43 and enters the engine 44 whereit is mixed with air and burned to generate electrical power as by meansof the dynamo 45 mounted on through a branch circuit 48-49 containingrheostat 50, to the heating member of furnace 41.

Coke from furnace 41 is delivered, with ore and flux from hopper or bin51, into the electrical heat drum 52 similar to that already described.This furnace is supplied with heating current from line wires 46--47, bybranch circuit 5354, containing a rheostat 55. Air is excluded fromdrumi 52, and reduction of the oxid ore with carbon is conducted at atemperature and pressure at which carbon monoxid gas is obtained,practically free from carbon dioxid. This substantially pure carbonmonoxid is withdrawn and taken into an engine 56 which is shown by wayof example in the diagram as operating upon the same crank shaft withengine 44, thus also generating electric power bymeans of the dynamo 45.Exhaust gases from engines 44 and 56 may be used for preheating the coaland the mixture of ore and flux, the exhaust pipes 5758 being indicatedas leading to the respective hoppers or bins.

The reduced metal and flux, according to the embodiment shown, isdelivered from 2. A method of reducing oxid ores which i comprisesreducing the oxid by means of carbon and heat w1th exclusion of,a1r, ata temperature and pressure less than atmospheric favoring the productionof carbon 7 monoxid,-removing the carbon monoxid and burning it tocarbon dioxid, and utilizing the available energy of the reaction todevelop and supply an electric current for furnishing heat to thereduction operation.

' 3. A method of oxid ore reduction comprising the reduction of the oxidby means of carbon and heat with exclusion of air at a temperature andpressure less than atmospheric that will substantially avoid formationof carbon dioxid and the consequent partial reoxidation of the ore orparts thereof, but will facilitate the production and removal of carbonmonoxid, removing and burning it to carbon dioxid and utilizing theavailable energy of the reaction to deduction operation.

5. A method of reducing oxid ores which comprises advancing a mixturecontaining oxid ore and carbon in heat conductive relation with anelectrical heating element while excluding air, and continuouslywithdrawing the resultant carbon monoxid from the locus of reaction.

6. A method of reducing oxid ores which comprises advancing a mixturecontaining oxid ore and carbon in heat conductive relation with anelectrical heating element while excluding air, withdrawing theresultant carbon monoxid gas from the locus of reaction and burning itwith air in a gas engine, translating the available heat energy thereofinto electrical energy, and utilizing the electrical energy forsupplying said'heating element.

7. A method of reducing oxid ores which comprises advancing a mixturecontaining oxid ore and carbonin heat receptive rela-v tion with anelectrical heating element while excluding air, withdrawing the re-isulting carbon monoxid gas and burning it with air in a gas engine,utilizing the resulting mechanical energy to produce electrical energyfor supplying'said heating element, and using the sensible heat of theexhaust from said engine to preheat the said oxid ore. r

8. In a system of reducing oxid ores the combination of a reducingelement constructed to reduce the oxid ore by means of ,carbon and heatwith exclusion of air at a temperature and pressure less thanatmospheric that Will facilitate the production and removalof carbonmonoxid gas, a gas engine actuated by said gas, and an electricgenerator driven by said enginefor generating heat 'ijor said reductionoperation.

-9. In a sy'stcm ofreducing oxid ores the' combination of a reducingelement which vreducesthe oxid ore by means of carbon and 'heat withexclusion. of air and at less than atmospheric pressure'in such mannerthat substantially pure-carbon monoxid .gas is given off by thereaction, a gas engine actuated by'burning sa1d gas with a1r, and meansfor preheating said oxid ores from the exhaust of said gas engine.

.' 10. A method'of reducing oxid ores which comprises" reducing the oxidby means of carbon and heat with exclusion of air, regulating thetemperature and pressure within the limits required to produce carbonmonoxid and substantially avoid the forma tion of carbon dioxid,removing said carbon monoxid, burning it to carbon dioxid, and

utilizing the energy of the reaction to de-.

velop and supply heat to the reduction operation.

11. In a system of reducing oxid ores the combination of a reducingelement constructed to reduce the oxid by means of carbon and heat withexclusion of air, at a temperature and pressure less than atmosphericthat will facilitate the production and removal'of carbon monoxid gas, agas engine operated by said gas, an electrlc generator' actuated by sa1denglne, means for preheating said ore by the exhaust from said gasengine and an electric refinin furnace operatively connected to said reucing element and said electric generator.

12. A system of reducing oxid ores electro-thermally with exclusion ofair, in which carbon or ore or both act as a conductor for the heatingelectric current and are heated largely by the passage of said currentthrough them, in combination with automatic means 'for maintaining thedelivery of carbon monoxid gas-therefrom.

13. In an electro-thermal system of re ducing oxid ores'by means ofcarbon and heat, the combination of a source of electrical energy, areducing element constructed to receive the ore and carbon and providedwith electrical heating means for heating the ore and carbon largely bypassing an electric current through them, said ore and carbon acting asan electrical conductor therein, and means in said reducing elementadapted to independently maintain the flow .of electric current andconsequent heating in case of an open circuit or partial open circuit inany part. of the body of said ore and carbon.

14:. A method of reducing oxid ores comprising rotating a 1. etorthaving an electrical heating element therein, passing a suitable-mixture of .ore and carbon therethrough and heating said mixture bysaid electrical heating element so as to produce the metal of the ore,"carbon monoxid gas and the residuum.

15. A method of.reducing-oxid ores comprising rotating a retort havingan electrical heating element therein, passing a suitable mixture of oreand carbon therethrough and heating said mixture by said electricalheating element with exclusion of air so as to produce the metal of theore, carbonmonoxid gas and the residuum.

16. Apparatus for reducing oxid ores with carbon and heat, comprising arotatable receptacle for said ores, an electric heating elementassociated with said receptacle, and means for deriving from thecarbonaceous gas, resulting from such reaction, an electric current forenergizing said heating element.

17. The method of reducing ores, which comprises advancing a mixturecontaining the ore and carbon across and in contact with successiveportions of an electrical heating element, While excluding air, andcontinuously withdrawing the resulting carbonaceous gas.

18. The method of reducing oxid ores which comprises advancing a mixturecontaining ore and carbon across and in contact with successive portionsof an electrical heating element, while excluding air, continuouslywithdrawingthe resultant carbon monoxid gas from the locus of reaction,burning it with air in a gas engine, translating the available heatenergy thereof into electrical energy, and utilizing the electricalenergy for supplying said electrical heating element.

. bon monoxid gas from the locus of reaction,

burning it wlth air in a gas engine, trans-' lating the available heatenergy thereof into electrical energy, and utilizing the electricalenergy for supplying said electrical heating element.

20. The method of reducing ores which comprises continuously feeding andtumbling a mixture containing finely divided ore and carbon in the formof a relatively shallow body through and in contact with a rotatinghelical electric heating element, while excluding air, continuouslywithdraw-- ing the resultant carbon monoxid gas from the locus ofreaction, urning it with air in a gas engine, translating the availableheat energy thereof into electrical energy, and utilizing the electricalenergy for supplying said electrical heating element.

21. The herein described metallurgical process which compriseselectrically heating coal with exclusion of air to produce combustiblegas and coke, burning the gas to produce electric power, and utilizingthe coke for reducing ore.

22. The herein described metallurgical process which compriseselectrically heating coal with exclusion of air to produce combustiblegas and coke, mixing the coke and ore, electrically heating the mixturewith exclusion of air to reduce the ore while again generatingcombustible gas, and burning the gas from both sources to produceelectric power for the system.

23. The herein described metallurgical process which compriseselectrically heating coal with exclusion of air to produce combustiblegas and coke,'mixing the coke and ore, electrically heating the mixturewith exclusion of air to reduce the ore while again generatingcombustible gas, electrically refining the metal, and burning the gasfrom both sources to produce electric power for the system.

GUYON F. GREENWVOOD.

